Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a first image in a sequence for a display screen or portionthereof with transitional graphical user interface showing our newdesign; and,

FIG. 2 is a second image in a sequence thereof.

The broken lines in the figures depict portions of the graphical userinterface which form no part of the claimed design.

The outermost broken line showing of the display screen or portionthereof is for environmental purposes only and forms no part of theclaimed design.

The appearance of the graphical user interface sequentially transitionsbetween the images shown in FIGS. 1-2. The process or period in whichone image transitions to another forms no part of the claimed design.

CLAIM We claim the ornamental design for a display screen or portionthereof with transitional graphical user interface, as shown anddescribed.